Mixing head for mixing fluids, in particular gases and/or liquids

ABSTRACT

A mixing head to be mounted on a utilization system is operable to mix media and to then supply the mixed media to the utilization system. The mixing head includes a housing having an inlet end and an outlet end. The outlet end has an annular flange to enable the housing to be mounted on the utilization system. A rotor is mounted within the housing for rotation about an axis. The rotor includes an upstream axial flow impeller and a downstream radial flow impeller. Each impeller includes plural rigid and fixed blades. At the outlet end of the housing is an outlet in the form of an annular gap to supply mixed media from the housing into the utilization system. A deflection hood is mounted at the outlet end of the housing. The annular gap is positioned radially outwardly of the hood. The hood has an outer surface that is directed away from the housing and that has a convex shape.

BACKGROUND OF THE INVENTION

The invention relates to a mixing head for mixing fluids, in particularvarious gases and/or liquids in a hot or cold environment.

EP-0 344 498 A2 discloses an impeller where, as alternative toconventionally used bucket wheels or blower wheels revolving in ahousing, chain-like link elements are used for generating a rotation gasstream. Such blower in particular is used in the pneumatic transportionof dust, chips and cuttings such as accumulate in wood and plasticprocessing. Such blower also can be used in the field of heating, forexample for flue gas conveyance, and the chain-like link elements servein particular for the purpose of reducing cleaning of the blower,especially if the gas to be conveyed is strongly loaded with dust. Insuch known blower it is furthermore suggested that a deflecting surfaceoppose the drive side to prevent gases inflowing centrally from escapingaxially. This ensures that the gas stream through the blower must bemoved into the rotation path of the rotating link chain so that a mixingof the gas stream results, in particular by being swirled by thechain-like link elements.

Such movable chain-like link elements however can tear, particularlyduring the starting phase of rotation, or they can become jammed oneagainst the other. Also, with vertical mounting of the link head, duringa starting phase until the chain rings have become opened, considerableloading of motor bearings occurs since the chain rings, until they arecompletely opened, are largely imbalanced. Furthermore no possibilitiesfor adding further fluid components are provided.

EP-0 473 618 B1 describes a similar blower which comprises a blowerwheel or impeller with a central hub and elements fastened thereon andmovable with respect to one another. Such elements are in the form ofchain pieces in order to achieve a spiral or worm-shaped gas stream in adevice for combusting bio or solid substances.

EP-0 525 711 A2 also discloses a device for the combustion of bio orsolid substances by a channel and a similar link head fan whose outletis directed into the interior of a gas or fire tube.

A mixing device which supplies an axial air stream against the directionof flow of a spiral-shaped rotating gas stream of wide area is knownfrom EP-A0 340 859 A2. As is the case with known mixing devices,however, such device is insufficient or lacking with respect to abilityto change mixing components.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a dynamically operatingmixing head which can be adjusted to change mixing tasks in order toachieve intensive thorough mixing and homogeneous mixtures withouthaving to accept the disadvantages in moving parts.

This object is achieved by provision of a mixing head including animpeller achieving axial flow positioned before an impeller achievingradial flow, in the stream direction.

Such arrangement provides an axial drawing-in of the fluid to betransported as well as also a radial acceleration thereof, thusproviding intensive swirling. Through this combination of impellersachieving axial flow with radial flow, the blades of which arepreferably fastened on a common hub, an effective through-mixing resultswhich can be achieved for various gases and/or liquids, e.g. the mixingof additives and air can be achieved sufficiently in the area of ahousing of the head. Thus, a second gas component can be suppliedthrough an admixing port disposed on a front face with the drawing intaking place by means of the axial flow impeller. This means that themixing device can also be used in installations which are not operatedat underpressure. On the other hand, outside of the region of rotationof the radial flow impeller, i.e. essentially at the peripheral boundaryof the mixing head housing, several nozzles can be provided, for examplefor adding liquid additives so that several components can be mixed intothe carrier fluid which, in general, is air.

A stationary deflection hood is disposed in the direction of flow afteror downstream of the rotation region of the radial flow impeller and hasguide elements, particularly guide channels, extending outwardly in thedirection of rotation. In contrast to the known deflecting surfaceaccording to EP-0 344 498, in which gas present is deflected through theguide elements extending outwardly in the direction of rotation, gasesflowing back are already guided in the rotational direction of rotationwhich prevents unchecked turbulence in the marginal region of theflowback premixer. This flowback premixer is formed as a deflection hoodin the shape of a hemisphere and is especially advantageous.

Further embodiments are characterized in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is described and explained in thefollowing in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross section through a mixing head; and

FIG. 2 is a top view of a rotor disposed in the mixing head.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a mixing head 1 according to the invention comprisesessentially a rotor 2 and a housing 3 which is affixed by an annularflange 4 on, for example, an air transport path of utilization system,e.g. a cylinder reactor or a cylinder muffle furnace. Housing 3 hasinlets 17, 18 into which medium is passed.

The rotor 2 comprises two impellers or blower wheels disposed one behindthe other in the axial direction. One impeller generates an axialthroughflow by means of obliquely inclined blades 5. The other impeller6 generates a radial flow by means of blades 7 oriented axially. Theblades 7 and the blades 5 are mounted on a common hub 8 of a shaft 9adriven by a motor 9.

In a preferred embodiment, the blades 5 and 7 are constructed to beexchangeable, for example they are detachably fastened by plugconnections on the hub 8. The blades 7 can have different crosssections, for example triangular, planar or oval. The selection ofmaterial of blades 5 and 7 depends on the media to be mixed. The blades5 are obliquely inclined and the degree of inclination depends on thequantity to be transported of the medium to be drawn in. For suchpurpose, the length and width of the blades 5 also can be varied. Thus,it is possible, e.g. if a relatively large transport stream is to begenerated, to employ blades 5 with a greater width and/or length. Forbetter mixing, the blades 7 can deviate from a smooth surface and cantherefore be perforated or ribbed.

The housing 3 at the axial side or end thereof opposite an inlet end hasa conical or semiconical deflection hood 10 located centrally of housing3 and rotor 2. Hood 10 forms a back-flow deflector of flow. The outersurface of hood 10, opposite the side facing rotor 2, has guide elements11 curved radially outwardly and backward in the direction of rotation.These guide elements 11 deflect the mixed medium flowing back towardmixing head i in the axial direction. The deflection hood 10 preferablyhas the shape of a conical or semiconical calotte the diameter of whichis a function of the application environment and of the media to bemixed.

The deflection hood 10 can have a greater diameter than the impeller 6.An annular outlet 12 for the fluid mixture or gas mixture preferably isin the form of a lateral gap if the deflection hood 10 has a greaterradius than the impeller 6. If the deflection hood 10 has a smallerradius than the impeller 6, the outlet 12 preferably is an annular gap.To improve flow, for example of very viscous media, guide blades 16 canbe disposed in gap 12.

The deflection hood 10 preferably is secured by columns 13 that may haveconduits 15 for cooling. Depending on the particular conditions, wateror thermal oil can be used as coolant.

Outwardly of the rotation area of impeller 6 are provided nozzles 14 forintroducing liquid additives. Liquid mist at the outer ends of theradial blades 7 immediately is rent apart and mixed with the gas stream.In preferred manner, the nozzles 14 are oriented tangentially to a planeof rotation of blades 7 in order to utilize optimally the suction of therotating medium. On the other hand, orienting the nozzles in a moreradial orientation enables choking or regulation of the suppliedadditive to be effected. The nozzles 14 are preferably protected throughpipe-shaped ports which can be attached to the conduits 15 for coolingthe nozzles 14.

To introduce liquids which are under high pressure, for example liquidfuel, a nozzle 14' is directed into the apex of the deflection hood 10and is connected to a feed line 19 extending through housing 3.

I claim:
 1. A mixing head to be mounted on a utilization system andoperable to mix media and to then supply the thus mixed media to theutilization system, said mixing head comprising:a housing having a mediainlet end and a media outlet end, said media outlet end having anannular flange to enable said housing to be mounted on the utilizationsystem; a rotor mounted within said housing for rotation about an axisextending in an axial direction from said inlet end toward said outletend, said rotor comprising an upstream axial flow impeller and adownstream radial flow impeller, relative to a direction of media flowfrom said inlet end to said outlet end, each said impeller includingplural rigid and fixed blades, whereby said rotor achieves intenseswirling mixing of the media within said housing; said housing having atsaid outlet end thereof an outlet in the form of an annular gap forsupply of the mixed media into the utilization system; and a deflectionhood mounted at said outlet end of said housing with said annular gapbeing outwardly of said hood, said hood having an outer surface directedaway from said housing, said outer surface having a convex hemisphericalor conical shape.
 2. A mixing head as claimed in claim 1, wherein saidouter surface of said hood has guide elements.
 3. A mixing head asclaimed in claim 2, wherein said guide elements are curved radiallyoutwardly and backwardly in a direction of rotation.
 4. A mixing head asclaimed in claim 1, wherein said hood is mounted to said housing bycolumns.
 5. A mixing head as claimed in claim 4, further comprisingcooling conduits for cooling said columns.
 6. A mixing head as claimedin claim 1, further comprising nozzles for introducing additive to aposition outwardly of said blades of said radial flow impeller.
 7. Amixing head as claimed in claim 6, wherein said nozzles are covered byconduits.
 8. A mixing head as claimed in claim 6, wherein said nozzlesare oriented tangentially of a plane of rotation of said blades of saidradial flow impeller.
 9. A mixing head as claimed in claim 1, furthercomprising at least one inlet port at said inlet end of said housing.10. A mixing head as claimed in claim 1, wherein said blades of saidaxial flow impeller and said blades of said radial flow impeller areattached to a common hub.
 11. A mixing head as claimed in claim 10,wherein said blades are exchangeably attached to said hub.
 12. A mixinghead as claimed in claim 1, further comprising guide plates positionedin said annular gap.
 13. A mixing head as claimed in claim 1, whereinsaid outer surface of said hood has formed therein guide channels.